The common octopus, Octopus vulgaris Cuvier, 1797 is a key species of economic interest among the halieutic productions in Senegal, consequently to an invasion in large quantities and a demographic proliferation in the marine waters of the country, at the beginning of the eighties. To explain the phenomenon, we have considered interesting to know the role of the species in the local ecosystem through its trophic relationships with the environment. During researches made from 1996 to 1998 along the Senegalese shore and owing to trawlings, 459 O. vulgaris, were collected. The stomach contents were analysed according to classic methods, especially qualitative and quantitative. Throughout the year, O. vulgaris regularly fed on benthic organisms and teleosts. Cannibalism was rather rare and the intraspecific competition to be occasionnal. In its environment, O. vulgaris found all the preys that contributed to its development and corroboted by the relation size-weight relationship......